I guess a single space isn't technically 'blank' but it sort of is. :) I was going to also try testing leaving comments but you have those blocked on posts that are older than x days old and the latest one is from ~5 years ago.
I'll have to pull that old code out and fix those things. It's not really a problem that your username is " ", I think. But it might get whitespace removed to "", which could be unfortunate. (UPDATE name SET name="Erik_" WHERE name=" " becomes UPDATE name SET name="Erik_" WHERE name="" and now Erik_... more
Rule #7 is what led me to find the bug- Erik_,Wed Aug 30 2023 10:34am
just a single space alone. Two spaces was rejected as already being registered. You've got a new post to play with. I guess I could have turned on commenting on another post, maybe I should do that too.
For strings? Java also has someString.isBlank() which returns true if the string is empty or only spaces. In Perl you can do something like: if ($some_string =~ m/^\s+$/) { # you gotta blank string }